Simulation Study on Electromagnetic Wave Propagation Law of Valve Side Bushing Partial Discharge in Converter Transformer
The main insulation of converter transformer valve side bushing is generally made of multi-layer metal winding and filled with epoxy impregnated paper.The propagation path and attenuation law of electromagnetic wave inside the valve side bushing is not clear.This seriously restricts the development of non-contact online monitoring technology for valve side bushing.At present,the non-contact partial discharge detection method represented by radio frequency and ultra-high frequency methods can effectively monitor the insulation state of the equipment by studying the propagation attenuation law of electromagnetic waves inside the equipment.In order to study the propagation attenuation law of electromagnetic wave in the valve side bushing,this paper constructs the actual±800 kV converter transformer valve side bushing finite difference time domain three-dimensional model.The propagation path and law of electromagnetic wave excited by partial discharge inside and outside the valve side bushing are also simulated and analyzed.The results show:1)The frequency band range of electromagnetic wave propagating to the outer space of the valve side bushing is 1.5～2.5 GHz.The first wave of electromagnetic wave in the external space appears at the flange,which is proved by experiments.2)The propagation path of electromagnetic wave inside the valve side bushing is the epoxy impregnated paper between the capacitor screens and the outer SF6 filling area.Electromagnetic waves propagate independently between capacitor screens and can be superimposed on each other after transmitting the capacitor core.3)In the outer space of valve side bushing,the space-time distribution characteristic of electromagnetic wave is that the electric field intensity decreases with the increase of time and distance.The specific attenuation law is nonlinear with distance.The attenuation range of electromagnetic wave after passing through the capacitor core is 14.11～47.47 dB/m.The attenuation range in external space is 2.74～13.07 dB/m.The results can provide technical basis for monitoring and diagnosis of partial discharge in valve side bushing of converter transformer.
valve side bushingpartial dischargeelectromagnetic wavefinite difference time domain methodpropagation law
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